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TUNNEL KILN.

Application led May 17,

To all whom t may concern:

Be it known that l, GEORGE HILLARD BEN- JAMIN, residing at New York, county of New York, State of New York, have invented a certain new and useful Improvement in Tunnel Kilns, of which the following is a specification.

My invention relates to improvement in tunnel kilns of the mule type. The object of my invention 1s a construction by reason of .which a more perfect temperature control is obtained than is possible in kilns as heretofore constructed. In tunnel kilns of the Dressler type, such for instance, as is disclosed in U. S. Patent No. 1,023,628, datedApril 16, 1912, gas and air are burned in combustion chambers located on each side of the interior of the furnace and the heat generated by such combustion is radiated by the walls of the combustion chambers. In such construction shown, the gas and air is introduced into the forward end of each chamber, and the products 'of combustion withdrawn from the rear end of such chambers. ln practice it is found that the high est temperature is at the point of entrance of the gas and air. This is not objectionable, but requires careful supervision of theI gas and air supply, to prevent over-heating at the forwardend of the kiln.

To avoid this objection, the constructiondisclosed in the patent of Benjamin, No. 1,268,204, dated June 4. 1918, was designed,

and wherein the combustion chambers 5,

on each side of the furnace, are divided into a series of combustion chambers, separately supplied with gas and air. rIhis construction effects better distribution fof heat, as the temperature zones along the interior of the kiln can be regulated as required. No one of these constructions, however, made any provision for the regulation of theA heat radiated from the surfaces of the combus-l tion chambers towards the goods carried through the kilns. ln practice if the heat radiated from the'combustion chambers at any point along high, the effect will be to burn or vcheck the surface of the goods transmitted through the kiln. It is, therefore, desirable to provide means for regulating the' heat along any portion of the length of the kiln, so as to obtain uniformity of heating.

In ,1y improved construction, the heating chambers on each side of the kiln are divided interiorly into two combustion cham- Specication of Letters ratent.

the length of thekiln is too l in position,

Patented May 9, 1922.

1921. semi No. 470,233.

bers, each of which is fed withgas and air, and each of which or both of which 'may be used to heat the air circulating around said chambers, and radiated from the opposed surface of the oppositely located heating chambers towards the goods in the kiln,

which arrangement permits a very perfect i regulation, not only of the whole temperature of the kiln, but of the temperature eX- hib1ted along the sides of the kiln, towards the goods moving through the kiln.

The accomp-anying drawings will serve to lllustrate my invention, in which Fig. 1 is a vertical section taken along the line I-I of Fig. 2.

F1g. 2 is a longitudinal section taken along the line lI-II of Fig. 3, and

.F ig. 3 is a horizontal section taken along the line Ill-III of Fig. 2.

Referring to the drawings, 5 indicates the body of the kiln which may be of any suitable construction. goods chamber 6 are heating chambers 7. Two` of such chambers are shown arranged longitudinally on each side ofthe goods chamber. The chambers 7 each consist of an outer enclosing wall 8, and two -closed combustion chambers 9 and 10.v The combustion chambers 9 and 10 are separated'v from the enclosing wall 8 and from each other in such manner as to form a' passage. The combustion chambers 9 and 10 are fed through separate as and air burners 11 and 12, which project into the chambers at one end. The products of combustion from such chambers pass out through flue 13 to chimney stack not shown. The heating chambers 7 are mounted above the` bench 14 of the kiln in such manner as to provide -an airspace around them and underneath them, the object of which arrangement is to permit circulation of the heated vapor intheinterior of the chamber 6, around the heating chambers 7 and through the goods. as indicated by the arrows in Fig. 1. lt will be understood that no air is introduced into the goods cham-.

ber of the kiln after the goods carriages are is due to the air in the kiln, which is heated from the combustion chambers. The air as it is heated passes upward in the-direction indicated by the arrows, then downward v'and under the combustion' chambers, the circulation being continuous. This circulationg it may be pointed out, isthe same as that described in the prior patents of Dressler,

and that the heating of the goodsv Located within the rea Benjamin and others, and no point oit novelty is claimed therefor.

rllhe circulation of air within the heating chambers 7 .is effected through the instrumentality of a blowe'r 15, the air being introduced through a duct 16, and passes through the spaces between the outer surface' of the chambers 9 and 10, and the eni veloping wall 8, andl then downward through the space between the chambers 9 and 10, and to the pump through the duct 17. The pump is provided with an air inlet duct 18 and'an air relief valve 19, so that the passage of the air within the enveloping chambers 7 may be maintained constant, or modified as desired. 20 indicates a goods carriage and 21 goods on the carriage to be treated. 22 represents slide valves which may be used to control the air fed to the interior ofthe chambers 7, and which, it will be understood7 may be used with the supply and relief valves of the pump 15.

The operation of my improved kilnv is as follows 1f the full temperature is tobe generated, both the burners 11 and 12 are put into operation and combustion takes place in the chambers 9 and 10. llt, however, it is desired that less heat be radiated from the inner sides of the heating chambers 7, which are opposed yto the goods, the burners 11 are put into operation and combustion takes place in the chambers 9. lli a higher heat i is required, thepburners 12 are put into operation; if a still 'higher heat, burners 11 and 12. 1F urther, it a high temperature is required at the entrace ot the kiln, the pressure of the gas and air introduced by the burners 11 and l2 may be low, in which lcas f combustion takes place at the entrance end" of the combustion chambers 9 and 10. llfv it is desired that the ltemperature be highest at the center of the kiln, the gas and air pressure are increased. Thus, by manipulating the burners 11 an 12, 'and varying the gas and air pressure, the temperature atthe entrance and middle of the kiln, and consequently at the exit entrance of the kiln can be regulated as desired.

It will be seen that when the burners in chamber 10 are not in operation, thel surface of this chamber, opposed to the goods side of the chamber 7 is cooled by the incoming air; Whereas thesurface of chamber 9 is radiating heat, which heats the air passing through the exterior of the heating chamber, andwhich is directed through the goods on a carriage 20.` lt will be further observed that the temperature of the air circulated by the blower 15 will depend upon whether or not one or b oth of the burners 9 or 10 are in operation. 1n practice, the air circulated by means of the blower 15 vmay be entirely omitted, and circulation effected in any other well known manner.

Having thus described my invention, l claim z- 1. A tunnel ovencomprising a main chamber through which goods to be heated can be caused to travel; a heating chamber on each side Aof the main chamber, butstructurally independent of the walls thereof; each heating chamber consisting of an enclosing structure and two structurally independent combustion chambers located therein.

2. A tunnel oven comprising a main chamber through which goods to be heated can be caused to travel; a heating chamber on each side of the main chamber, but stru@ turally independent of the'walls thereof; each heating chamber consisting' of an enclosing structure and two combustion chambers located therein structurally independent.

and spaced as regards each other and the walls of the enclosing chamber.

3. A tunnel oven comprising a main chamber through which goods to be heated can be caused to travel; a heating' chamber on each side ot the main chamber, but structurally independent of the sid.; walls and roof of the main chamber; said heating chambers each divided into two separated combustion chambers located therein and an air circulating chamber, together with means for introducing combustible gases into the said `combustion chambers separatelyn and means for circulating air around said combustion chambers.

4t. A tunnel oven comprising a mais; chainber through which goods to be heated can be causedto travel; a heating chamber on each side of the main chamber and structurallv independent of the side walls thereof; each heatlngchamber consisting ot' an enclosing structure and two structurally independent, spaced. heating chambers located therein, 'together-With means for introducing a com- GEORGE HILLARD lBlCNJ'AltllN.y Witnesses FLORENCE A. Cnorrtn, D. Marne.

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